Electrical apparatus



Aug. 18, 1931. c; B. c o A'rEs ET AL. 1,319,148

ELECTRICAL APPARATUS Filed March 21, 1928 INVENTORS Ch IF/PJ B. (cafes ATTORNEY.

40 to give details regarding what'metal or metalh ft hb n in broken outline, the section 90 Patented Aug. 18, 1931 1,819,148

' UNITED STATES PATENT OFFICE CHARLES B. COATES CLARENCE J. DRESSER, OF CLEVELAND, OHIO, ACSIGNOBS 1'0 CHICAGO PNEUMATIC TOOL COMPANY, 01 NEW YORK, N. Y., A CORPORATION OF NEW JERSEY ELECTRICAL APPARATUS Application filed March 21, 1928. Serial No. 263,564.

This invention relates to electrical apparabe devised for determining the end ring areas tus, particularly electrical motors of the a which would give substantially maximum reternating current induction type without sults with the chosen alloys. cominutators or brushes. More specifically When the experimental work was begun, 5 it relates to an improved form of rotor for it was found that better results could be obsuch motors, especially small motors for electained with an aluminum alloy than with trical tools of the portable or hand type such pure aluminum. Trials with an aluminum as are used for drilling, tapping, reaming, alloy containing copper were encouraging. riveting, screw driving, nut running, stud Good results were secured with aluminum 1o setting, etc. alloys containing from l% to 16% of copper Among the objects of the invention are to with best results at 8% to'10% of copper. improve the performance, to increase the r On account of the difference in conductivity, liability and to avoid certain weaknesses in the cast conductor bars of t e rotor had to be motors for portable electrical tOOlS, to demade approximately two times the size of the velop a rotor for such tools characterized by copper conductor bars or coils ordinarily used 65 hi hsustained speed, high torque, indestructin a motor of given capacity. Hence the ibi ity and reduced weight, to determine shape of the slots in the rotor core became upon suitable alloys for cast windin s' and important and extended tests established that end rings for securing the above resu ts and slots expanding toward theperiphery of the to fix uponthe relative proportions and d1- core with substantially radial sides gave the mensions of the winding and ep d rm 5- necessary bar area without excessive impalr- Other objects will be apparent fromthe ment of the magnetic densities of the teeth .tailed description which follows. of the rotor core. Open slots were found to While it has heretofore been proposed to be preferable in that this arrangement mini- 5 construct rotors having the conducting leads mized the zigzag leakage between the teeth 75 or bars and the end rings in one piece, 110 of the' rotor core. The area of conductor attempt has been made to adapt the same ,having been established, a formula was for use with. P t han p rated tools eventually worked out for determ ning the where power. and sustained high speedt cross sectionaharea of the end rings, this gether with light weight are important facformula containing a constant K w th a so tors under the exacting requirements of prespreferential value of .4 but-with a permissive out day mass production methods. U. S- variation of from .36 to 46 without serious Patent No. 1,647,633, issued November 1, impairment of'the operating characterlstios 1927 to C. E. Johnson, proposes to use an aluof the motor.

minum 3" cast d g and end g In order to illustrate the invention a conbut for motors above 5 H. P. and with fea crete embodiment thereof 15 shown in the tures intended to reduce the amount of curn i g draw ngs m which: required i-n h Prior I Fig. 1 is a longitudinal sectional view however including the J 0 son patent fails througl the improved rotor with aremova e lic'alloy should be used for the casting operabeing taken substantially on the broken line tion and what the bar and end ring areas 1 1 f Fi 2,

must be if the". cast rotors are to equal or to F1 2 i t sverse sectional view sub exceed the performance of motors havlng stan'tially on the line 2-2 of Fig. 1, the shaft 45 rotors of standard construction, i. e., with bar b i itt d, o or wire windings. By extended experimen- A i di t d th otor core is made up of tation and research work the more desirable a plurality of iron plates 3 providing a lamialloys for the sp ific purpose w deternated structure, which plates have a series o mined upon and duriu the d vel pm nt slots 4 disposed symmetrically adyacent their period it was discovered t at a formula could peripheries. Each slot has a restricted openwith th in this ing through the periphery thus leaving teeth 5 of substantial size on the plates alternating with the slots therein. The plates are assembled in face engagement with the slots 4 thereof in substantial register in accordance e usual practice. While maintained position, conductor bars 6 and end rings 7 integral with the rods 5 are cast in one piece and in one operation upon the armature core 3.

If the casting is to be done in sand molds an alloy of aluminum with from 4% to 16% of copper is used, the preferred alloy containing aluminum 92% to 90% and copper 8% to 10%, the molten alloy being arranged to enter at the bottom of the mold and to the laminated core body 3 expelling the air and other gasses ahead of the molten metal. If the rotor is to be die cast the copper content of the alloy may be reduced and silicon added. A preferred alloy giving substantially the results of the preferred aluminum copper alloy with the same bar and end ring areas consists of aluminum 94 copper 2%%, silicon 3%.

s shown in Fig. 2, the. slots in the core plates are of substantial size, being formed to contain substantially two times as much of the cast alloy as of copper either in bar or Wire form. To secure an opening for such an increased mass of the conducting material without reducing permissible magnetic densities of the teeth 5 between the slots 4, each slot is relatively small and rounded toward the axis of the armature and the cast alloy as indicated, the alloy and the certain cross sectional area were required and it was found to be possible to determine such area very exactly for motors of differing sizes and capacities by the formula anK from .36 to .46 with but slight effect upon the operating characteristics of the motor. A preferred shape of the cast end rings 7 "shown as tapered the aligned slots 4 in is illustrated in Fig. 1, wherein the rings are annuli having their bases upon the end rotor tplates and wholly covering the slots 4 save or the restricted pen heral openings thereof between the teet 5 of the plates.

' Rotors constructed in accordance with the present invention and utilizing the aluminum alloys herein specified, are much lighter than copper bar or wire wound rotors. are substantially indestructible and the integral union of the cast bars and end rings makes any loosening of the rotor plates, such as occurs with copper bar rotors, wholly impossible. Likewise and for the same reason the unfortunate effects of a loosened coil in a wire wound rotor are avoided. An additional advantage results from the smooth contour of the improved rotor, particularly when provided with tapered end rings as shown which prevent dirt and grit from lodgin on the rotor and cutting through the stator windings as happens with motors used in grinding and other abraiding or polishing operations. Most important is the fact that rotors formed in accordance with the present invention and utilizing the alloys and the proportioned dimensions herein disclosed are found to develop greater horse-power, higher torque, and a higher sustained speed than corresponding copper bar and wire wound rotors.

While the invention has been herein disclosed in what is now considered a preferred form, it is to be understood that the invention is not limited to the exact details thereof but covers all changes, modifications and adaptations within the scope of the appended claims.

We claim as our invention:

1. A rotor for induction motors having a slotted core and having conductor bars and end rings cast in one piece upon said core of an alloy comprising approximately nine number of poles of the by .4. i

2. A rotor for induction motors designed for high sustained speed and high torque, said rotor having a slotted core and having said rings being m cast in one piece ing of substantial size in cross section and co'verd as to their outer portions by said core save for a narrow part which extends to and forms a part of the peripheral surface of the rotor the form of annuli spaced from the eriphery of the rotor and from the rotor 5 mil: with wide bases engaging the ends of said core and covering the y. portions of said bars, said rings. extending outwardly from said core with smooth converging tapered sides and terminatin in'rounded ends thereby to cause dust an grit to be thrown off so as to through of stator windmg.

Si ned by us at Cleveland in the count{ u ahoga and State of ()hio, this 17t day 0 March 1928.

,CI-iARLES B. .eoa'rns.

CLARENCE conductor bars and end rin upon said core, said bars prevent the cutting J. DRESSER. 

